Auxiliary axles and wheels are today commonly used in wheeled vehicles especially on trucks and trailers for selectively more evenly distributing the vehicle load onto the road surface. The auxiliary axle not only increases safety but also provides for a means to conform with highways weight capacity laws. Because the auxiliary axle and wheels are only needed while carrying heavier loads, many different assemblies and apparatus have been devised for selectively raising the auxiliary axle and wheels when the wheeled vehicle is operated in an empty or lightly loaded condition and for lowering the auxiliary axle and wheels in contact with the road surface when operating under a heavy loaded condition.
Lift axle assemblies are typically attached to the frame of the wheeled vehicle in the "pusher" position between the vehicle back driven wheels and the front steering wheels or the "tag" position behind the back driven wheels. A frame including a pair of hanger brackets are attached to the wheeled vehicle frame and extend downwardly therefrom. One or more arms are pivotally attached to the hangers and extend toward the rear of the vehicle whereat they are also attached to the auxiliary axle. A pair of springs, typically air springs, are located between the auxiliary axle and the vehicle frame in a manner whereby at least a part of the vehicle load can be transferred from the frame through the support air springs and to the auxiliary axle and wheels. The support air springs are selectively filled or energized with air for effectively partially transferring the vehicle load therethrough. For raising the auxiliary axle and wheels, the support air spring is de-energized or deflated and a lift mechanism is provided for pivoting the support arms upwardly and thereby raising the auxiliary axle and wheels off of the road surface and up underneath the wheeled vehicle frame. Typically, the lifting mechanism utilizes a lift air spring which is selectively inflated when the support air spring is deflated thereby causing the auxiliary axle and wheels to be lifted. The lift air spring is deflated when the support air springs are inflated for allowing the auxiliary axle and wheels to be lowered onto the road surface. Examples of such prior lift axle assemblies are shown and described in Gottschalk et al., U.S. Pat. No. 5,403,031 and Van Raden et al., U.S. Pat. No. 5,230,528.
The prior art lift axle assemblies, however, are not without drawbacks, shortcomings and limitations. The present invention addresses these limitations of the prior art along with today's requirements and needs for providing a more compact, durable, long lasting and relatively low cost lift axle assembly for effectively and efficiently lowering the axle and wheels in the in use position for transferring part of the vehicle load through the axle and wheels to the road surface and for efficiently and easily raising the auxiliary axle and wheels up and under the wheeled vehicle frame when the auxiliary axle and wheels are not needed.